This invention relates to hand tools. More particularly, it is concerned with a hand tool for removing knockout rings from electrical sheet metal enclosures.
Many sheet metal boxes or enclosures employed in electrical wiring systems have knockouts of standard sizes which may be selectively removed to permit the passage of cables or conduit. Typically the knockouts are discs which are severed from the sheet metal of the enclosure except for a tab at a small portion of the periphery. In order to permit the same knockout to be used for cables or conduits of different sizes the center knockout disc may be encircled by one or more concentric knockout rings. Typically each knockout ring is held in position in the sheet metal of the enclosure by two diametrically opposed tabs.
In the usual manner of preparing a box for a conduit of large size an electrician would first use a screwdriver to knock out the center disc of the knockout. Then a screwdriver would be used to pry loose and bend up one side of the first knockout ring encircling the opening left by removal of the center disc. This step would be repeated to pry loose and bend up the other side of the ring. Next the electrician would use a pair of pliers to twist the bent ring back and forth until it would break out by fracturing the tabs. This procedure was time consuming and required a certain amount of manual dexterity. Frequently the ring would break leaving a portion of a tab attached to the enclosure which would have to be removed in order for the conduit to fit in the opening.